1. Latent Class Analysis of Behavioral
Predictors for HIV/STI Infection among
Patients at the Miriam Hospital
Immunology Center
Allison Greenwald, Gaeun Gena Yoo, Michael Leung
Who Needs PREP?

2. Purpose
• To investigate the demographic and behavioral
patterns of patients who test positive for HIV.
• To create risk profiles for men who have sex with
men (MSM) to identify individuals who are most
likely to be at highest risk for infection, and
therefore, would benefit most from access to HIV
pre-exposure prophylaxis (PrEP).

3. Hypotheses
1. Participants engaging in risky sexual behaviors, such as
having anonymous sex, having sex under the influence of
drugs and alcohol, using injection drugs, having forced sex,
exchanging sex for money, having sex with someone of
unknown HIV/STD status, not using condoms, or having a
more than 1 partner per year are more likely to be part of a
high risk group associated with HIV and other STDS
1. Specifically, participants who engaged in anonymous sex,
exchanged sex for money and did not use condoms would
be especially likely to fall into high risk groups
2. Relative to their risk group, we expected participants to
underestimate their risk of HIV infection.
1. We expected African Americans to be the mostly likely to
present in high risk groups as according to the CDC, “African
Americans are the racial/ethnic group most affected by HIV
in the United States.”

4. The Sample
• 348 Men who have Sex with Men (MSM) or Men
who have Sex with both Men and Women
(MSM/MSMW) who presented at the Miriam Clinic
between January 2013 and February 2014.
301
47
MSM MSM/MSF
Gender of
Sex Partner
7
74
67
50
28
22
41
30
14
16
0
20406080
Frequency
0
16-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60+
AGEGROUP
Distribution of Age Group
219
43
36
11
40
0
50
100
150
200
250
White Hispanic Black Asian Other
Race / Ethnicity

5. Statistical Methods
• Latent Class Analysis using Data collected on an
Immunology Form
– Behavioral Variables
• Sexual Behavior
– Having engaged in anonymous sex
– Having engaged in sex while under the influence of
alcohol/drugs
– Having sex with someone who has unknown STI status
– Having forced sex.
• Condom Use
• Drug Injection
• Sex Exchange
• Logistic Regression/Chi Square Analysis to examine
demographic class differences (covariates)

6. LCA Results
• A comparison of model fit indices identified that a 4
class model fit best and provided 4 distinct groups

7. • Class 1 is the “highest risk group” in all
categories except for anonymous sex
– Anonymous sex (86.1%)
– Having sex under the influence of alcohol/drugs
(73.9%)
– Sex with People of Unknown STI Status (63%)
– Exchanged Sex for Money (29%)
– No Anal Condom Use (93.8%)
– No Oral Condom Use (95.9%)
– More than 6 partners (88.1%)
– Use of Injection Drugs (19.4%)
*Percentages within class
Class 1: Highest Risk Group (Behaviors)

8. • 66 individuals
• Age and Race/Ethnicity Class Breakdowns
• Higher than average populations of
– Race/Ethnicity classified as “Other” (ex. Cape Verdean, Native
American)
– Age 20-24 and 30-39
• Class 1 has the second largest of population of bisexuals (24%
within class, 34.8% of the population)
• Class I has 3 members who have tested positive for HIV
(5.56% within class)
Class 1: Highest Risk Group
(Demographics)

9. • Class 4 is a “high risk group” with an extremely
high rate of anonymous use and lack of condom
use
– Anonymous sex (100%)
– Sex with People of Unknown STI Status (62.3%)
– No Anal Condom Use (61.5%)
– No Oral Condom Use (95.9%)
• As compared to class 1, fewer individuals have
more than 6 partners
– More than 6 partners (20.3%)
– Primarily have 2-5 partners (61.6%)
*Percentages within class
Class 4: High Risk Group
(Behaviors)

10. • 118 individuals
• Age and Race/Ethnicity Class Breakdowns
• Higher than average populations of
– Race/Ethnicity self-identified as Black and Asian
• Class 4 has the largest of population of bisexuals (36%
within class, 41.3% of the population)
• Class 4 has 2 members who have tested positive for HIV
(1.92% within class)
Class 4: High Risk Group (Demographics)

11. • Class 2 is a “moderate risk group” with no
engagement in anonymous sex but also high
levels of unprotected sex
– Anonymous sex (0%)
– No Anal Condoms (78.6%)
– No Oral Condoms (84.2%)
• They are distinct from other classes in that they
are lower in terms of other sexual behaviors
– Sex with People of Unknown STI Status (24.5%)
– Exchanged sex for drugs/money (1.6%)
– Having 2 to 5 partners (48.3%)
*Percentages within class
Class 2: Moderate Risk Group
(Behaviors)

12. • 143 individuals (Largest Class)
• Age and Race/Ethnicity Class Breakdowns
• Higher than average populations of
– Race/Ethnicity self-identified as Black and Hispanic
– 15-19 and 40 – 59
• Class 2 has the a small population of bisexuals (8% within
class, 23.9% of the population)
• Class 2 has 2 members who have tested positive for HIV
(1.67% within class)
Class 2: Moderate Risk Group
(Demographics)

13. • Class 3 is a “low risk group” with no or few
partners
– 0-1 Partners in the last year (100%)
– Sex while under the influence of alcohol/drugs (13.8%)
– Injection Drug use (0%)
– No Anal Partners (100%)
– No Orals Partners (97.1%)
Class 3: Low Risk Group (Behaviors)

14. • 21 individuals  smallest class
• Age and Race/Ethnicity Class Breakdowns
• Not distinct racially in terms of overall population
• Higher than average population of people within the ages
of 15 to 19 and 50+
• Class 3 has no bisexuals
• Class 3 has 1 members who have tested positive for HIV
(7.14% within class)
Class 3: Low Risk Group (Demographics)

15. Findings: HIV/PrEP/STDs
• There is no statistical significance between any
class and HIV status or STD/STI status
• There is no statistical significance between any
class and any particular age or racial/ethnic group
• This lack of statistical significance is likely attributed
to a small sample size and an especially small HIV
positive population
• Based on our findings, we cannot make any
recommendations for which class is mostly to
benefit from PrEP

16. • Class 3, our “low risk group” believed they had
low risk of HIV infection
• Over half of class 1, our “highest risk group”,
identifies as medium to high risk.
• Class 2 and Class 4 our “high risk group” and
“moderate risk group” underestimate their
medium and high risk with most individuals
saying they believed they were at none or low
risk
*While these findings are interesting, they are based on our subjective assessment of
which groups are high and low risk, and not rooted in our statically significant findings
Findings: Perceived Risk

17. Limitations/Suggestions
• Continue to collect data using the current or an even
more detailed/more specific immunology form
– Make sure patients answer all questions, as there was a fair
amount of missing data
• This could be achieved using a computer program which doesn't’t allow
the individual to move on until the question has been answered?
• Increase sample size!
– In order for the study to be effective, it must include more
individuals who have tested positive for HIV
– It will also allow for
• Increased precision in estimation and greater confidence in
the results
• Inclusion of variables which had too many missing values or
too few individuals who reported “Yes” such as blood
tranfusion/organ transplant, intranasal cocaine, incarceration,
tattoo, hepatitis C